I just think this is way too complicated for any single rule, and it's going to be impossible to administrate case-by-case, which is why the CSA was brought in to start, one rule for all.
I can't see a way to force NRP to pay without affecting children. If they have children they currently live with, putting them in prison will affect those children, possibly leaving them in poverty- which I believe did happen in Canada for a while.
I do agree with 50/50 start, so no one is defined as RP, and work back from there, rather than the current method of assuming one RP has full time care, then calculating how much the NRP's CS is reduced by. I don't like the definition of overnights either- one parent could care for the child 7 am until 9pm, 7 days a week, but the other would be "RP" because they are present while the child sleeps.
Again the problem with 50/50, and defining by overnights is in most separations the NRP is left without a suitable home for overnights.
I am trying to think how you could possibly prevent or insure- increase taxes on the higher earning parent per child, then use that money as a savings pot that can be accessed by a RP only if household income drops below threshold, or when the child turns 18?
I also wonder how we provide for children of single parents who have no other parent- as a young child whose dad dropped dead, there was no CS to chase, my mum was completely on her own. I had a friend who would moan about the amount her nrp paid, and wonder why she seemed not to get my situation, no money, not ever. If CS is so needed, how to we support parents who can't get CS- death, disability, incapacity....